Melamine aldehyde, urea aldehyde, and melamine-urea aldehyde copolymer solutions are available in acid colloid form. These materials are meta-stable and are electrolyte sensitive. Known melamine aldehyde, urea aldehyde and melamine-urea aldehyde solutions including melamine formaldehyde solutions (MF solutions) are not stable above pH 4. In contrast, colloidal silica solutions (C.S. solutions) are not stable below pH 5. Thus, there is an apparent incompatibility in blending these products.
Although resins and gels of melamine formaldehyde and silica have been reported in the literature, resins and gels are not useful as paint detackifiers. Gel formation is generally associated with a significant drop in detackification coagulation or effectiveness.
MF solutions and colloidal silica have both been reported to be effective paint detackifiers. However, until the present invention, a single product blend was not available because of the different pH ranges where the two components, the MF solution and colloidal silica, are stable. U.S. Pat. No. 4,863,165 describes a method for paint detackification employing low molecular weight cationic polymers and silica. The related patent, U.S. Pat. No. 4,929,382, claims compositions of low molecular weight cationic polymers and silica. Notably absent from the claims and examples of U.S. Pat. No. 4,929,382 and U.S. Pat. No. 4,863,615 are the compositions wherein the low molecular weight cationic polymer is melamine formaldehyde, or other melamine aldehydes, urea aldehydes or melamine-urea aldehydes.
U.S. Pat. No. 4,863,615, discloses a method for treating pain kill waters comprising melamine formaldehyde and colloidal silica solution. However, the disclosure of U.S. Pat. No. 4,863,615 reveals that the melamine formaldehyde and the silica must be kept separate prior to being used in the system and fed separately into the system. The incompatibility of melamine formaldehyde and the related aldehydes with silica had precluded the formation of a single blend composition.
The present invention provides for stable blended compositions of melamine, urea, or melamine-urea aldehyde and colloidal silica; solutions formed of materials previously believed to be incompatible.